This invention relates to an apparatus and method for inspection used in the analysis of defects in semiconductor devices, and more particularly to an apparatus and method for inspecting semiconductor devices capable of effectively detecting defects in an LSI of smaller size, higher density, and higher integration.
As LSI devices become higher and higher in integration, it becomes difficult to find the location of defects by an electrical analysis alone by using an LSI tester. Accordingly, it is necessary to measure and directly observe the electrical state of the internal circuit of an LSI device.
Conventionally, for this purpose, a mechanical probe was directly fitted to the Al wiring pattern inside the LSI device, and the electrical state was measured to discover a defect location. In this method, however, as the LSI became smaller and smaller, it has become difficult to place the mechanical probe correctly on the Al wiring inside the LSI device, and it can no longer be applied to today's high integration LSI analysis. Besides, the distributed capacitance in the mechanical probe or wiring may deteriorate the precision of measurement.
Recently, to solve the above-discussed problems, research and development are being concentrated, for example, into electron beam probes by applying an scanning electron microscope (S.E.M.) as disclosed in pages 172-201 of Nikkei Electronics 3-15, 1985, and this technology is applied in the analysis of an LSI device. This device is intended to observe, without making contact, the electrical state inside the LSI device, by aiming electron beams at the surface of an LSI device placed in a vacuum, and detecting the secondary electron signal released from the LSI device surface, and it can be advantageously applied to micro-sized LSI device.
On the other hand, an attempt has been made to develop a laser probe to analyze the internal state of an LSI device by reducing the laser beam into a small focus and aiming it at the LSI device. This method is used to analyze, without contact, the logic state inside of the LSI device in the atmosphere, instead of in a vacuum.
With these two contactless probing means, however, it is extremely difficult to pinpoint the defect location in a large LSI device.
When analyzing a defect in an LSI device by using the contactless probing technology, it is necessary to probe from the external terminal where an LSI device fault trouble has been detected sequentially toward the inside of the LSI device, and judge if the result of probing is correct or not. In this case, in today's LSI device, since its circuit scale is enormous, it is next to impossible to probe all of the tremendous member of nodes and judge each result. It is therefore considered effective to probe and judge only the node (a specific portion of the internal circuit) considered to be related to the LSI defect. However, it is not efficient to determine which node should be probed depending on the symptom of the LSI defect and judge the result every time using manual labor. Besides, only those having sufficient knowledge of the LSI circuit composition and pattern configuration are qualified to select the node to be probed and judge the result of the probing.